With flourishing advancements in technologies, various information products are developed to satisfy people's different needs. In early days, the majority of displays are cathode ray tube (CRT) displays. However, because of their huge size and power consumption as well as health concern due to radiation exposure for long-term users, CRT displays are replaced gradually by liquid crystal displays (LCDs) at present. LCDs own the advantages of lightness, thinness, shortness, smallness, low radiation, and low power consumption. Thereby, they have become the main stream of the market. Currently, in order to achieve the characteristics of large size, color, thinness, lightness, and low power consumption of LCDs, high-performance light sources have to be developed.
LCDs are non-light-emitting displays. Thereby, in the environment with bad light conditions, illumination methods have to be applied. For example, LCD in a watch utilize a simple light bulb for illumination; those in automotive meters or OA terminals adopt light sources from back of the LCDs for clear displays. The thin and white light sources used this way are named backlights. LCDs according to the prior art use color filters to display the three primary colors of a pixel and hence colors can be displayed. A pixel of such LCD with color filter is composed of three subpixels corresponding to red, green, and blue color filters, respectively. Human eyes receive the red, green, and blue lights passing through the color filters and mix them to form the color of the pixel. However, color filters will affect transmittivity of light through the LCDs. Besides, they also influence the dot size of a pixel in LCDs. Thereby, the resolution of LCDs is limited by color filters.
In order to improve resolution and transmittivity problems described above, color sequential LCDs are developed. Color sequential LCDs according to the prior art display sequentially the three primary colors of a pixel to form color. In this color sequential LCD, each pixel uses three light sources to emit red, green, and blue lights, respectively, as the backlight. In a frame time, the pixel displays three data sequentially corresponding to lighting red, green, and blue lights, respectively. By taking advantage of the visual staying phenomenon of human eyes, people can identify the color of the pixel. In comparison with LCDs with color filters, color sequential LCDs do not need to use color filters and thus the dot size of a pixel in the latter LCDs is smaller than that in the former LCDs. Accordingly, color sequential LCDs can reduce costs and enhance resolution.
Color sequential LCDs display images according to the scan signal and data signal produced by the control circuit thereof. Besides, each pixel of such color sequential LCDs displays color images by using light sources of three primary colors emitting red, green, and blue lights in the same frame as backlights, respectively. Thereby, each scan signal has to scan each of the color backlights in a frame time. For example, if the control circuit produces two scan signals, then the two scan signals have to scan red, green, and blue backlights, respectively. The scanning method according to the prior art is that a sequential red-, green-, and blue-backlight cycle is completed in a scan signal cycle. Namely, after a scan signal scans the red, green, and blue backlights sequentially, the next scan signal continues to scan the next red-, green-, and blue-backlight cycle. However, such a scanning method will result in color mixing between two adjacent color backlights, because it scans sequentially red, green, and blue backlights. That is to say, in a single scan signal, the red backlight will mix with the linking green backlight, and the green backlight will mix with the linking blue backlight. Two color mixings will occur in each scan signal. Consequently, the number of color mixings in the scanning method according to the prior art increases as the number of scan signals increases, reducing quality of color images displayed on color sequential LCDs.
Accordingly, the present invention provides a circuit for controlling a color sequential liquid crystal display and a method for scanning the same, which can improve the color-mixing problems in a color sequential liquid crystal display according to the prior art, and can solve the problems described above.